The present invention relates to an apparatus for unfolding an antenna netting reflector. Such reflectors comprise stiff ribs which are pivotally supported and which extend radially outwardly from a center in the unfolded condition of the antenna netting reflector. The netting of the reflector is secured to the ribs and suspended between the ribs.
Such antenna reflectors are primarily used in space travel because it is essential in space vehicles that the payload is as large as possible having regard to the limited transport volume. Thus, these antennas are initially folded when the space vehicle travels towards its intended orbit. Only when the intended orbit has been reached, will the antenna be unfolded. Several different constructions are known in the art for such folding antennas. These prior art structures comprise various types of unfolding mechanisms adapted to particular requirements, see for example the publication "Zeitschrift fuer Flugwissenschaft und Weltraumforschung", Number 4, 1980, Volume 5, pages 255 to 267. A so-called "offset" reflector is disclosed in this reference among others. Such reflector may be unfolded and has the above mentioned features. The unfolding takes place in two sequential phases. In the first unfolding phase flexible cross connectors are effective which are secured between the rib ends. These flexible cross connectors are kept under tension during the folded condition of the reflector. When these flexible cross connectors are released they start the unfolding of the reflector by spreading the radial ribs. The full unfolding takes place in the second phase which also provides for a locking in the unfolded position. Such locking is necessary to assure a defined surface configuration of the reflector netting. Such locking requires an additional drive means because during or along the last portion of the unfolding displacement a counteraction is required for opposing the increasing tension in the reflector netting. The prior art structure provides for this purpose an adjustment motor which operates block and tackle means. However, the structural details of such block and tackle means are not described in the above mentioned reference.
The flexible cross connectors which are secured to the rib ends in the prior art reflector construction are exposed to extraordinarily high mechanical tensions, especially when the ribs are in their folded condition resting closely next to one another. Moreover, during the starting or launching of a space vehicle, vibrational energy is introduced into the reflector structure which must be taken up additionally by said cross connectors. These extraordinarily high loads are a source of trouble or danger because they may cause one or the other cross connectors to break even before the unfolding operation begins, whereby a proper unfolding is not assured anymore.